Vibrating and other separatory screen assemblies are generally known in the art and are very useful in accomplishing the separation of materials on the basis of size of the materials to be separated. A slurry of liquid and entrained solids will be caused to run or flow across an upper surface of a screen panel assembly. Particles of a certain size and above will not pass through apertures in the screen panels and will thus be separated out. The screen panel assembly is caused to vibrate by a suitable means, with this vibratory motion being beneficial in facilitating the proper separation of the material directed onto the screen panel.
One such vibratory screen panel assembly is shown in U.S. Pat. Nos. 5,112,475 and 5,277,319, both to Henry, and both assigned to Conn-Weld Industries, the assignee of the present application. In these two patents, there is disclosed a screen panel mounting system for a vibrating screen assembly, and a screen panel which is securable in the vibrating screen assembly using the panel mounting system. A plurality of screen panels are secured to a panel deck of a frame portion of a vibrating screen assembly. A plurality of elongated hold downs or center retainers, which are made of a resilient elastomeric material, such as polyurethane, are provided with spaced anchoring pins along their bottom surface. These anchoring pins are receivable in apertures in an anchor member. Once the hold down members or center retainers have been secured to the anchor member, which is, in turn, attached to spaced cross members or tubes of the frame of the vibratory separator, the screen panels are placed atop the panel deck with their side edges in contact with the center retainers. Elongated key members are inserted into upwardly facing slots in the center retainers to spread wing portions of the retainers laterally outwardly. This spreading of the wings of the center retainers causes the wings to grip the side edges of the screen panels so that these panels are secured in the vibrating screen assembly.
The panel mounting system disclosed in the two above-referenced Henry patents, which are assigned to Conn-Weld Industries, utilizes screen panels and cooperating anchor members which are bolted, welded or otherwise secured to cross members of the panel deck of the vibrating screen assembly. An owner of a vibrating screen apparatus which is not provided with the appropriate anchor members disclosed in the prior Henry patents must make substantial revisions and modifications to his vibrating screen assembly if he is to be able to enjoy the advantages of the Conn-Weld Industries panel mounting system.
A center retainer assembly for a panel mounting system is disclosed in U.S. Pat. No. 5,398,817 to Connolly et al. and also assigned to Conn-Weld Industries. The center retainer assembly described in the '817 patent utilizes an elongated bolting bar which is encased in a resilient material and which includes an elongated center retainer. The center retainer assembly is placed into an upwardly facing retainer channel and is secured to the retainer channel by placement of the bolts carried by the bolting bar through holes in the retainer channel. The retainer channel is, in turn, secured to mounting plates that are attached to a cross tube or to a cross bar of a vibrating screen assembly.
A more recent screen panel retainer system is described in the U.S. Pat. No. 6,964,341 to Bacho, et al., which is also assigned to Conn-Weld Industries, the assignee of the subject patent application. In that system, the screen panels are held in place by screen panel edge strips that have pockets on their undersurfaces. Those pockets are cooperatively shaped to receive a plurality of ears that are situated on upper surfaces of retainer bars. These retainer bars are connected to the underlying screen stringer rails. While the screen panel retainer system described in the Bacho et al. patent has found acceptance in the industry because it does not require modification, or re-working of the industry standard screen stringer rails, it has been found to be somewhat difficult to use and has required the provision of screen panel edge strips which have been less easily installed than would be desired. Adjacent screen panels have required the use of cooperating and abutting screen panel edge strips. This alignment and abutment has been somewhat difficult to obtain in the field and has increased the time that has been required to initially install the system and to then replace worn screen panels with replacement screen panels. In an industrial setting, the amount of time that is required for a machine to be out of service, for repair or refurbishment results in a loss of production capability. Such lost production time should obviously be kept to a minimum. In the screen panel retainer system described in the Bacho et al. patent, these times were not able to be minimized to the hoped for degree.
The need still exists for a separatory panel retainer system that is compatible with current industry standard vibrating separatory machines and which can be quickly and expeditiously installed and maintained. In addition, the separatory panel retainer system must have the capability to accommodate to both new machines, as well as to older, used machines. The screen stringer rails which are secured atop the cross tubes or cross bars of the typical vibrating separatory machine, are typically configured with spaced holes along their upper faces. These spaced holes are used for the attachment of the screen panels to the machine's frame.
When the machine is new, all of the holes on the screen stringer rails are of uniform size. A number of currently available screen panel retention systems depend on the proper dimensioning of those holes to accomplish the securement of the screen panels to the machine frame.
Vibrating separatory machines are frequently used in applications in which a relatively abrasive material is separated from a suspension fluid, such as water. The slurry of fine abrasive particles and the suspension fluid finds its way into all of the components of the screen assembly, including into the spaces that exist between the screen panel connection mechanisms and the holes or apertures in the screen stringer rails. Over the course of time, the slurry abrades the holes and causes them to enlarge. This abrading action is enhanced by the vibration to which the separatory machine is continually subjected.
Eventually, these holes in the screen stringer rails become enlarged. Since a number of the currently available panel retainer systems utilize some type of an interference fit of pins, pegs or the like into these holes, the enlargement of these holes is problematic. At some point, the stringer rail holes become so enlarged that they will no longer engage the pins or pegs with sufficient retentive force. At such time, the screen stringer rails have to be refurbished, the screen panel retainers have to be modified or the screen stringer rails simply have to be replaced with new rails. In each such instance, the process involves considerable work and the equipment being taken out of service.
The prior Bacho et al. U.S. Pat. No. 6,964,341 addressed this issue by the use of self-expanding polyurethane plugs. These plugs are expandable radially by the tightening of a bolt to radially expand a polyurethane sleeve which is initially sized to be insertable into the conventionally spaced and sized holes in the screen stringer rails. The snap lock screen panel and retainer system in accordance with the present invention continues to utilize this feature of the prior Bacho et al. system. Improvements have been made so that the threaded bolts which cause the expansion of the polyurethane plugs, cannot be tightened so that they will strip out the expander nuts which are pulled up toward the center retainer bar to expand the polyurethane sleeve radially.
A need thus exists for a screen panel retainer system that uses a minimum of parts, that is tolerant of dimensional variations and that is quick and easy to install and use. The snap lock separatory panel and retainer system in accordance with the present invention overcomes the limitations of the prior art and is a substantial improvement over the presently available systems.